Northumbria University Jun 18 2025 Evidence of the permanent impact of smoking on people's teeth has been uncovered by researchers for the first time. Researchers from Northumbria University have discovered that smokers have tell-tale signs of their smoking habits ingrained deep within their teeth, which remain even after a person has quit. PLOS One, could help to shine new insights on forensic and historical investigations. Teeth consist of three main hard tissues: enamel, dentine and cementum.